2007 R320 CDI

This has been one of those projects where simply nothing goes right.

I took the car to the best Indy shop in my small town, well known for Mercedes work. They said the alternator and both (main & aux) batteries were bad and needed to be replaced. Quoted $305 for the alternator, a total of $1100 for the job.

I told them to go ahead. They called me back a few hours later, said the price on the alternator was wrong, it was $450. Ok. They called back later and said they couldn't get one at that price, it would be $650.

I said screw that, take out the alternator and give it to me, I'll have a 30-year alternator rebuild shop fix it. They said they did not recommend that, but let me have it.

The alt shop said the voltage regulator was bad, ordered a new one. When it came in, it was bad from the factory, so they ordered another. When I picked it up, they said the regulator wasn't "exactly" the right one, but it should be OK. My Indy put it back in the car.

I took it to AutoZone for an electrical test, said the main battery was bad and the alternator has excessive voltage ripple. I ordered a new battery from Interstate $300, and said it would be 11 days before it got here. Eleven days go by, I call them to pick up the battery. They say its on back order, don't know when, maybe 1-3 weeks. I go get my money back.

Go to NAPA order the battery for next day delivery for $200. That is today.

This morning I decide to study up on voltage ripple because the Indy told me in the beginning that the R320CDI is very sensitive and the electronics can be damaged with a bad alternator, and rebuilts are rarely correct.

Yup, voltage ripple is a serious issue for electronics. Its near certain that the installed rebuilt alternator will need to come out and I don't even have the new batteries installed yet. When its running again, in a day or two, I'm taking it back to the alt shop to see if they will stand behind their work and make this right.

The only possible jury-rig solution is to install a "smoothing capacitor" to tone down the ripple. Some VWs have one of these caps factory installed near the fuse box, but there doesn't seem to be much other info.

Does anyone know something about smoothing capacitors?

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1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI